The present invention relates generally to an image pickup system such as a silver-salt or digital camera, and more particularly to an image pickup system comprising an electronic view finder suitable for use with a compact image display device, especially a reflection type liquid crystal display device.
Most of silver-salt or digital cameras comprise means for recording images pickup up by an image pickup optical system and a viewing optical system for checking an image pickup range. For the recording of images, chemistries on film surfaces are used in the case of silver-salt cameras, and information obtained through photoelectric conversion at electronic image pickup devices such as CCDs are employed in the case of digital cameras.
On the other hand, most of viewing optical systems are of the type designed to form an image on the retina of a viewer's eye, thereby viewing the image to be picked up. This type of viewing optical system does or does not comprise an image pickup optical system for forming an image to record a part of the entrance side. A typical example of the former is a single-lens reflex camera, and that of the latter is a real image type finder suitable for use on a zoom optical system, including an objective optical system, an image-erecting means and an eyepiece optical system and now mounted on most products. These are often collectively called an optical finder.
In many cases, digital cameras or video cameras are put on the market while they are provided thereon with an electronic finder designed to display an image on an LCD (liquid crystal display device) rather than an optical finder, so that the image pickup range can be checked by allowing an observer to have a direct view of the image. Digital cameras with both an optical finder and an electronic finder mounted thereon, too, are now commercialized.
Furthermore, the so-called EVF (electronic view finder) designed to view images on LCDs via a viewing optical system is proposed. For conventional commodities with such an electronic finder mounted thereon, there is used a display device with a display screen having a diagonal length of about 0.5 inches or 12 mm.
However, there are growing demands for size reductions of cameras. The associated viewing optical system has been designed in conformity with conventional LCD size; the whole size of the viewing optical system cannot be reduced or some limitations are placed on further size reductions of image pickup systems.
Meanwhile, some LCDs have been developed with size smaller than so far achieved. However, when such LCDs are used with an electronic view finder, existing viewing optical systems offer a problem that the angle of field for viewing subjects becomes small depending on LCD size so that satisfactory observation becomes difficult.
Further, as the whole size of a viewing optical system is reduced in conformity with LCD size, some inconveniences such as failures in obtaining the eye relief necessary for observation are unavoidable.
Furthermore, as the magnification of the viewing optical system increases with decreasing image display device size, not only is chromatic aberration of magnification likely to occur but there is also a problem that dust, etc. deposited on the viewing optical system is visible on an enlarged scale.
To add to this, when a reflection type display device with light rays incident on its display screen side is used as the image display device, it is required to get hold of the separate optical path necessary for display purposes.